Engine controller



May 17, 1955 A. w. GARDINER ErAL ENGINE CONTROLLER 12 SheetS -Sheet 1Original Filed July 6, 1942 $31M W W mi y 1955 A. w. GARDINER ETAL2,708,426

ENGINE CONTROLLER Original Filed July 6, 1942 12 Sheets-Sheet 2 (6'04III 294 Original Filed July 6, 1942 A. w. GARDINER ETAL ENGINECONTROLLER 12 Sheets-Sheet 3 y 1955 A. w. GARDINER EI'AL 2,708,426

ENGINE CONTROLLER Original Filed July 6, 1942 12 Sheets-Sheet 4 y 17,1955 A. w. GARDINER ETAL 2,708,426

ENGINE CONTROLLER l2 Sheets-Sheet 5 Original Filed July 6, 1942 May 17,1955 A. w. GARDINER ETAL 2,708,426

ENGINE CONTROLLER 12 Sheets-Sheet 6 Original Filed July 6, 1942 y 7,1955 A. w. GARDINER EIAL 2,708,426

ENGINE CONTROLLER l2 Sheeis-Sheet 7 Original Filed July 6, 1942 liw Qlam l w mm y 7, 1955 A. w. GARDINER EI'AL 2,708,426

ENGINE CONTROLLER l2 Sheets-Sheet 8 Original Filed July 6, 1942III/IIIIII/ wQ wam MW s NR k wil May 17, 1955- A. w. GARDINER ETALENGINE CONTROLLER Original Filed July 6, 1942 12 Sheets-Sheet 9 40th ZQUWham y 7, 1955 A. w. GARDINER ETAL 2,708,426

ENGINE CONTROLLER Original Filed July 6, 1942 12 Sheets-Sheet 10 DEGREES0F CAM MOVEMENT ENG/NE INTAKE PRESSURE INCHES 0F MERCURY Q 0&- 6R E6 OFTfi/QOTTLE- OPEN/N6 o a E v DEGREES F CAM Mm/E-ME/vr y 1955 A. w.GARDINER ETAL 2,708,426

ENGINE CONTROLLER Original Filed July 6, 1942 12 ShetsSheet 11 11$ .www@QI -2 1 1 F a Sf/ I Q5 Q5 1 Q 1 w x Wf w p N\ -3 1 1.\ 1 1 i mk y 7,1955 A. w. GARDINER ETAL 2,708,426

ENG INE CONTROLLER 12 Sheets-Sheet l2 Originalv Filed July 6, 1942,er'yro 2737121 W A United States Patent ENGINE CONTROLLER Arthur W.Gardiner and Arthur W. Gaubatz, Indianapolis, Ind., Willard T. Nickel,Rochester, N. Y., and John Dolza, Fenton, and Peter W. Perish, Pontiac,Mich., assignors to General Motors Corporation, Detroit, Mich., acorporation of Delaware Continuation of abandoned application Serial No.449,918, July 6, 1942. This application September 7, 1949, Serial N114,438

29 Claims. (Cl. 123-103) This invention relates to aircraft and theprimary object is to render the operation of aircraft more safe andeffective by simplifying the control of the engine and the propeller.More particularly, we aim to safeguard the engine from overboosting,from overspeeding and from improper setting of the carburetor formixture strength.

To accomplish these objects we provide an automatic engine controllercomprising an automatic manifold pressure regulator which is manuallycontrolled by a single control lever operated by the pilot for settingthe pressure regulator to maintain a selected manifold pressure inpredetermined relation to altitude. We provide means set by the controllever for adjusting mixture strength in coordinated relation to theselection of the manifold pressure. We provide means set by the controllever for controlling the setting of the propeller pitch adjusterwhereby a certain engine or propeller R. P. M. is selected incoordinated relation to the selection of manifold pressure. The enginethrottle valve is partly under direct control by the control lever andpartly under control by the automatic pressure regulator, the control bythe control lever being sufficient to control the throttle valve to makea take-01f or safe landing. We provide speed responsive means operatingthrough the automatic pressure regulator for effecting a closingmovement of the throttle valve when a certain engine or propeller speedis exceeded.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawings:

Fig. l is a side elevation of the device.

Fig. 2 is a side elevation viewed from the direction opposite to Fig. 1.The part shown in section is taken on line 2-2 of Fig. 9.

Fig. 3 is a plan view of the device.

Fig. 4 is an end view looking in the direction of arrow 4 of Fig. 1'.

Fig. 5 is an end view looking in the direction of arrow 5 of Fig. 1.

Fig. 6 isa viewpartly in vertical section on the line 6-6 of Fig. 4,illustrating particularly the pressurecontrolled mechanism forcontrolling the position of the carburetor throttle valve.

Fig. 7 is a detail sectional view on the line 77 of Fig. 5 showing aportion of the mechanism for controlling the mixture ratio and of themechanism for controlling engine or propeller R. P. M. (speed).

Fig. 8 is a detail section on the line 8-8 of Fig. 7.

Fig. 9 is a detail section on the line 9-9 of Fig. 7.

Fig. 9a is a detail section on line 9a-9a of Fig. 9.

Fig. 10 is a detail section on the line 10-10 of Fig. 6.

Fig. 11 is a detail section on the line 11-11.- of Fig. 1.

Fig. 12, is a detail sectionon theline 12-12 of Fig. 7.

Fig. 12a is a sectional view of a speed responsive switch.

Fig. 13 is a sectional view on the line 13-13 of Fig. 7'.

Fig. 14 is a detail section on the line 14-14 of Fig. 1.

Fig. 15 is a diagrammatic view illustrating the various pressurecontrolled mechanisms and the fluid conduits through which fluid underpressure is conveyed to the several pressure-operated devices.

Figs. 16, 17 and 18A are charts showing the functions of the device.

Fig. 18 is a diagram of the mode of operation of the device showingvarious positions of the throttle valve resulting from various positionsof the main control lever of the device.

Fig. 19 is a diagram showing the device connected with the pilotscontrol lever in the cockpit of the airplane, and the effect of movingsaid control lever into emergency throttle closing position.

Fig. 20 is a diagram of a certain movement of the ditferential lever ofthe device.

The framework of the device comprises two housings indicated genericallyby the reference numbers 2 and 4 which are secured together in anysuitable way, as by bolts 6. The housing 2 is provided with mounting pad7 adapted to be secured to the engine or to some other suitablesupporting means. The pressure operated mechanism for controlling theposition of the throttle valve is located within the housing 2 and themechanism for controlling the engine or propeller R. P. M. and the fuelmixture ratio is located Within the housing 4, these mechanismsoperating to position the several instrumentalities controlled therebythrough the medium of a system of levers principally located outside thetwo housings and supported thereby. Referring to Fig. 6, it will benoted that screws 10 secure to the housing 2 end plate or head 8 inwhich certain fluid passages are formed, for a purpose later set forth.

Referring to Figs. 1, 6 and 19, the carburetor throttle valve V isrotated by an arm 11 connected by a link 12 with the stud 13 of adifferential bell crank lever 14, by any suitable form of universaljoint 16. The lever 14 is enlarged to form a hub 15 to receive the outerrace of a ball bearing 17, the inner race of which is, supported by astud 17a carried by an arm 18 which is secured to a shaft 20 whichextends through the housing 4 and is suitably journalled for rotationtherein. The housing generically designated 4 comprises two parts, 22and 24, secured together by suitable machine screws 26 and bushings 27,which are secured between the parts 22 and 24 as shown in Fig. 12,provide bearings for the shaft 20.

The lower end 28 of the lever 14 is pivotally connected at 29 with alink 30 pivotally connected at 31 with a piston rod 32 attached in anysuitable manner to a piston 34 slidable in a cylinder 36 formed in thehousing 2. The piston 34 is normally held in the position shown in Fig.6 by a spring 38 located between the piston 34 and a cylinder head 40which is fixed in one end of the cylinder 36 and has a sleeve 42 formedat the center thereof to provide a bearing in which one end of thepiston rod 32 slides. Another cylinder head 44 is located in theopposite end of cylinder 36 and has formed thereon a. shoulder 46 whichis engaged by a portion 48 of the section 24 of housing 4 secured to thehousing 2 by screws 50. The cylinder head 44 has a centrally disposedcylindrical. extension 52 in which is received a bushing 54 whichprovides a second bearing for the piston rod 32. A suitable packinggland 56 is provided to prevent any leakage of fiuid around the pistonrod.

The. piston 34 and cylinder 36 constitute a servomotor for automaticallyoperating the differential lever 14-to1 move the throttle valve of thecarburetor in response to movements of the piston; and oil pressure, ascontrolled by an automatic valve and provides the motive power formoving the piston. To effect movement of the piston, oil under pressureis supplied to a passage (Figs. 1, 4, 10, 11 and 15) formed in the wallof the housing 2 from any suitable oil line leading to the engine whichline may be connected at 61 (Figs. 1 and 4). At a point intermediate itsends, the oil passage 69 communicates with a short passage 62perpendicular thereto and also formed within the wall of the housing andbest shown in Figs. 6 and 11. The passage 62 communicates with anannular groove 64 formed in the outer wall of a valve guide 66 whichforms the fixed part of a control valve hereinafter described in detail.The oil flows from the passage 64, as determined by the control valve,either through the orifice 68 which extends through the wall of cylinder36 and communicates directly with the space 70 within the cylinder atthe right side of the piston 34 in- Fig. 6, or into the passage 72 shownin Figs. 6 and 10, from which it flows through a horizontal passage 74,shown in Fig. 10, formed in the wall of the cylinder 36 to the port 76,through which it flows through the port 76 into cylinder 36 on the leftside of the piston 34, as seen in Fig. 6.

When oil under pressure is admitted through orifice 68 to space '70, thepiston moves to the left and the control valve permits oil to flow fromthe space at the left of the piston; and, vice versa, when oil underpressure is admitted by the control valve to passages 72, 74 and 76 tocause piston 34 to move to the right while oil is permitted to flow outthrough passage 68. In case of failure of oil under pressure, the piston34 is returned by the spring 38 to the position shown in Fig. 6, thuspartly closing the throttle valve. Return of the throttle valve to idleposition is effected by manual operation as will be described more fullylater.

The control valve includes the valve guide 66 previously referred to anda movable valve 80 slidable within the guide 66. The valve 80 is movablein a manner described more fully hereinafter by manually operablemechanism and automatically by devices movable in response to manifoldpressure. The position of the valve 80 controls the flow of oil to theopposite sides of piston 32 and, therefore, controls the movement of thepiston and the position of the throttle.

The valve guide 66 is fitted within a cylindrical bore 82 formed in theend wall of housing 2, the bore having a shoulder 84 formed thereonwhich is engaged by a flange 86 formed at one end of valve guide 66. Aspring 83 located between guide 66 and part 48 of housing section 24maintains the flange 86 against shoulder '84. As stated before, thevalve guide 66 has an annular groove 64 in its outer wall whichcommunicates with the passage 62 through which oil is supplied underpressure. Groove 64 is located between two other annular grooves 96 and92 in the valve guide 69. Grooves 64, 90 and 92 are connectedrespectively by ports 94, 96 and 98 with the interior of valve guide 66.As shown in Fig. 10, there are a plurality of each of the several ports94, 96 and 98 and the fiow through these ports is controlled by thevalve 80 which has provided on its outer surface two circumferentialribs or lands 100 and 102, which are spaced apart and have a sliding fitwith the inner wall of valve guide 66. As the valve 86 is moved by meanslater described, the position of the lands 100 and 102 with respect tothe several ports 94, 96 and 98 controls the flow of oil and theposition of the piston 34, by determining which of the ports 96 and 98are in communication with port 94.

For instance, with the parts in the position shown in Fig. 6, the valve80 is in such a position that the ports 94 and 96 lie between the twolands 100 and 102. In this position of the parts the oil, which entersunder pressure through passage 62, will flow through port 94 into thespace between the wall of the valve 80 and the inner wall of valve guide66 into passage 72, through passage 74 and orifice 76 into cylinder 36at the left of the piston 34. This would cause a movement of the pistontoward the position in which it is shown in Fig. 6.,

During this movement of the piston 34, any oil to the right of suchpiston would be forced out of the cylinder 36 through ports 98 into thespace within the right end of valve guide 66 and to the right of the rib102. This space is connected with the low pressure oil reservoir throughdrain passages 93, 9S and 124 (Figs. 1, 4 and 15) connected with a lowpressure return to the oil reser vorr.

If the tubular member 80 is moved far enough to the right for the ports94 and 98 to lie between the ribs 106 and 102, then the oil which entersthe passage 62 will flow inwardly through the port 94 and outwardlythrough the port 98 which communicates with passage 68 through which oilis forced into the cylinder 36 at the right of the piston 34, creating apressure thereon which will move the piston toward the left in Fig. 6.Upon such movement of the piston, oil lying to the left of the piston isforced out of the cylinder, flowing through port 76 and communicatingpassages 74 and 72 into the space between the tubular element 80 andguide 66 at the left of the rib 180. This space is in communication withthe interior of the main housing section 2 from which the oil flows backto the oil reservoir of the engine. To this end an orifice is providedin the housing just above the cylinder 36 that connects with asubstantially horizontal passage 122 which, in turn, connects with thevertical passage 124 as shown in Fig. 4. At its upper end, the passage124 communicates with a horizontal passage 126 which opens into thespace in the housing2, as shown in Fig. 6. When the engine is inoperation, oil may stand in the housing as high as the level of passage126, but when the engine is stopped, the oil in the housing 2 runs outthrough orifice 120 and the housing becomes empty.

The valve 80, during most of the time when the engine is in operation,occupies a position somewhere between the two extreme positionspreviously described, in which the port 94 is the only one of the portsin cylinder 66 which lies between the lands 100 and 102. With the partsin this position, there can be no flow of oil and. the piston 34 is in acondition of balance with no force tending to move it in eitherdirection, at whatever position it may have occupied when the valve 80moved to such intermediate position.

The movement of the valve 80 to different positions to perform thefunctions previously described is brought I about partly by manualcontrol means and partly by automatic control mechanism operable inresponse to changes in pressure within the engine manifold. In order tomove the valve element, a rod 130 is fastened to valve 80 and clevis132. The clevis 132 is pivotally connected at 134 to one end of a lever136 pivotally mounted on a pin 138. The other end of the'lever isengaged by a spring 140 which is received in a bore 142 formed in thewall of the housing section 2 and lies between the end of lever 136 anda plug 141 which is threaded in the end of the-bore 142. The spring 140causes the upper end of lever 136 to be urged against acam 144. The cam144 is rotated manually to determine the position of one end of thelever 136 and thereby to determine the initial location of the movablevalve 80, which valve is positioned also by the shifting of the pivotpin 138 of lever 136 by means (to be described) responsive to variationin manifold pressure. In order manually to rotate the cam 144, it issecured to, or may be integral with, one end of a shaft 146 as bestshown in Fig. 11. The shaft 146 is rotatably mounted in a cylindricalsleeve 148 which is journalled for rotation in boss 150 formed on theWall of housing section .2. For a purpose to be referred to later, theaxis of rotation of shaft 146 is normally located above theaxis ofrotation ofthe sleeve 148. The sleeve 148 is provided with a flange 152,one end of which is adapted to engage a shoulder 154 formed on thehousing wall, while an Operatin lever 1 ,6. s ecured to the sleeve 148.at the.

opposite end thereof; and, when the device is assembled, the. shoulder152, and the operating lever 156 which. is secured to the sleeve 148 bya screw 158, prevent any longitudinal movement of the sleeve. 1.48.

In order to rotate the shaft 146 which carries the cam 144, the shafthas secured thereto, at the opposite end thereof, an operating arm 16.0haying a flat 161 engaging a corresponding flat 162 on the shaft 146.Thus the operating arm is always secured. to the shaft 146. in the sameposition. The arm 160 has a. split clamping hub 163 which, when the armis properly positioned on the shaft, is tightened by a clamping screw164, so. as to be secured to the shaft 146. A clevis 166 is pivotallyconnected to the arm 160- by pin 168 placed in either one of two holes170 formed in the end of the arm 160.. The purpose of the two holes isto vary the. degree of angular movement of the shaft 160 for the samedegree of movement of the clevis 166. The clevis 166 is part of a rod.

or link 172, which is adjustable with respect to the clevis 166 and maybe setin any position of adjustment by the nut 174 (Fig. 2). Theopposite. end of the. rod 172 is pivotally connected with a lever 180having three holes 178, one of which may be selected to receive a pin176 passing through a clevis 177 in the end of rod 172. Lever 180 issecured by means of a clamping screw 182 to the knurled end of the shaft2.0 (left. end of shaft 20 in Fig. 12), which is rotatably mounted inbearings 27 retained by the walls of sections 22 and 24 of the housing4. The right end of shaft 20. (Fig. 12) is connected with the maincontrol lever, designated in its entirety by numeral 186, and comprisinga part 186a loosely journalledon shaft 20 and. a part I8 6 b attached toshaft 20 by a clamping screw 1860. When lever part 186a rotatescounterclockwise a spring 480 transmits motion to lever part 18,6!2.Spring 480 surrounds a stud 481 attached to lever part 186a and extendsthrough a hole in lever part 186.5 and receives a, washer 482 retainedby a. pin 483. Pin 483 limits the separation of lever parts,

186a and 1 .615. due to the, action of spring 480 which normally isunder compression. The-purpose of the construction of the main controllever, designated generally by number 1861, will be described later. Thelever 186 (Fig. 1) has one or more holes 187 for receiving a pin bywhich a link may be connected leading to the pilots control lever in thecockpit of the airplane. It will be apparent from the foregoing that,through the chain of connections described, lever 186 will move the cam144 to whatever position the pilot may select. As shown in Fig. 6,movement of the lever 186 also causes movement of the engine throttledue to the fact that, as shaft 20 is rotated, the floating fulcrum 17aof lever 14 is rotated about the axis of shaft 20.

If the pivot 138 of the lever 136 (Fig. 6) isstat-ionary when themovement of cam 144 takes place, the lever 136 and the valve 88. will bemoved a corresponding amount. Valve 88 can be moved by movements of pin138 along axis B-B, Fig. 6. The pivot pin 138 is carried by webs 190integral with adjacent discs 1912 and 194 to which the adjacent endedges of identical metal bellows 196 and 198 are sealed. The left endedge of bellows 196 is sealed to a disc 200 having a central stem 202received in bore in a tubular boss 204 of housing part 8. A screw 285passes through a plain hole in a bushing 288 threaded in boss 20.4. andthreadedly engages the stern 292. A nut 210, threaded on bushing 208,may be screwed against the boss 204 to hold the bushing 208 in aposition of adjustment for a purpose to be described. A nut cover cap211 isv secured between the head 206 of screw 205 and the bushing 2.08to prevent turning the nut 210 by a wrench and moreover to conceal thenut 210, thereby making it less likely that the adjustment of bushing208 will be disturbed after the apparatus leaves the factory. Byscrewing the adjustment bushing or sleeve 208 in or out, the pivot 138can be brought intosuitable connecting pipe, not shown.

the correct position relative to the. cam 144 and the. assembly of valveand guide 66.

The space within the bellows 196 is evacuated; and the collapsing of thebellows 196 is resisted by a heavy spring 212 and a lighter spring 214located between the discs 192 and 200 under certain states of initialcompression. The right end edge of bellows 198 is sealed to a ring 216secured by screws 217 to housing 2, there. being a gasket 218 betweenthe housing 2 and the ring 216. Ring 216 carries a spring retainer rin:19 en-- gaged by a spring 220 held under a certain. state of normalcompression between the disc 194 and, ring 219. The interior of bellows198 is connected with the engine manifold by a passage 222 in housing 2(Fig. 15) and a Spring 220 op-. poses collapsing of bellows 1958 asmanifold pressure. decreases.

The effective areas of the bellows 196 and 198. arev equal; thereforethe system will not be afiected by changes in pressure within housing 2.The movements. of pivot pin 138 bear approximately a linear (firstpower) relation to corresponding changes in pressure within bellows 198.By proper selection of the springs. 212, 214 and 270, the desiredmovement of thefpivot 1 138 as a function of pressure change withinbellows 198 is obtained.

The control by the lever 186. of the selection of enine or propeller R.P. M. will now be described with, reference to Figs. 7, l2 and 13. Fig.7 shows that shaft. 20 (operatedv by control lever 186) drives a segmentgear 23.0 which is. secured tov the shaft, for rotation therewith andmeshes with a gear 232 attachedv to a cam plate 234 rotatable on astationary rod 236. Plate 234 has a cam. slot designated generally by numeral 238 for receiving a follower roller 240 pivotally carried by anarm 242 integral with a yoke 24.4 straddling the plate 234 and integralwith trunnions. 246 and 248 journalled in bearings. 245 and 247,respectively, carried by housing sections 22 and 2.4. Trunnion 2,46,drives an arm 250 connected by any suitable linkage (not shown with acontroller which controls the propeller pitch changing mechanism inorder to obtain a, desired engine or propeller R. P. M. As will bedescribed later when the main control lever 186 is. moved the, cam 238produces such movements of the arms 242 and 250 that the relation ofmovement of lever 186 to the selected engine or propeller R. P. M. willbe a predetermined relation best suited to the operation of the; engineunder certain conditions. Curve p r of Fig. 17 is illustrative of thisrelation for a certain type of engine.

The control by the main control lever 186 of the. richness of the fuelmixture will now be described with. reference first to Fig. 7. Theperiphery of the. cam.

" platev 234 controls the operation of a servo piston 272,

which is movable to different positions toregulate the mixtureproportions in a manner to. be described. The; piston 272 is slidablewithin a cylinder 274 formed in the housing section 24. The cylinder 274is closed at one end by a threaded plug 276 which is screwed thereintoand limits the movement of the piston toward the right, said pistonbeing normally held in a position adjacent to. the plug when, the engineis not running, by a compression spring 278, received between the pistonand the opposite end of the cylinder. When. the engine is in operation,the piston is movable by oil pressure to determine automatically, withincertain limits, the setting of the mixture control.

To operate the mixture control mechanism, the piston is secured in anysuitable manner to arod 280. slidable in a bushing 282 fixed in thehousing section 24. The rod is connected at the opposite end to. an arm284 by a pin and slot connection. A slot 286 is formed in the lower endofthe arm 284; and the. piston rod 280 is bifurcated at the left, endthereof 7 to form a slot therein so that the slot 286 straddles the pin288 into which the end of arm 284 projects which extends across the slotin the piston rod.

The arm 284 is secured to an enlarged hub 292 on a shaft 294 which isrotatably journalled in bushings 296 and 298, between the upper andlower housing sections 22 and 24 (Fig. 8). The end of bushing 296 isclosed. The bushings have flanges 300 which are received, when the partsare assembled, between the housing sections 22 and 24 and flanges 302and 303 on the shaft 294, so that the shaft is prevented from axialmovement.

One end of shaft 294 is knurled at 304 and an arm 306 is correspondinglyknurled and secured thereto by a pin 308, or in any other suitable way.At its upper end, the arm 336 is pivotally connected to an adjustablelink comprising a clevis 310 and a rod 312 screwed thereinto andprovided with a lock nut 314 to hold it in any adjusted position withrespect to the clevis, so as to vary the length of the link as desired.The clevis is bifurcated at the end which is connected to the arm 306;and the flattened upper end 316 of the arm is received between the twoparts of the clevis to which it is pivotally connected in any suitableway to permit some lateral play at the connection as well as rotation inthe pivot. This rod 314 is formed with a rectangular cross section atthe opposite end and is then bifurcated to receive between the partsthereof a short flattened arm 320 which extends from a cylindricalmember 322. The arm 320 is pivotally connected by a bolt 323 which has aloose enough fit with the arm to permit some lateral as well as pivotalmovement.

The member 322 is rotatable on a sleeve 324, but is adapted to rotatetherewith to control the fuel mixture ratio. The sleeve 324 somewhatloosely surrounds the outer cylindrical surface of an elongated nut 325having a hexagonal socket 326 and screwed upon a stud 328 attached to arotatable member 330 which regulates the fuel mixture setting. Bytightening the nut 325, the sleeve 324 is clamped tightly against aplate 338, and the plate 338 against the member 330 so that the parts324, 338 and 330 will rotate together. Member 330 can be rotatedmanually by means connected with plate 338 or automatically through aconnection between arm 320 and sleeve 324. Since it is necessary toinsure that the parts 324, 338 and 330 be tightly clamped together inthe desired adjusted angular relation when the nut 325 is tightened, thereduced extension 332 of member 330 is provided with radial teeth 334which engage radial teeth 336 formed on adjacent face of the plate 338.Radial teeth 340 similar to the teeth 336 are formed on the oppositeside of the plate 338 and these engage corresponding teeth 342 on theflanged end of sleeve 324 so that, where the assembly of parts isclamped together, the two sets of teeth 334, 336 and 340, 342 engage toprevent any slippage between the parts 324, 338 and 330.

The connection between the arm 320 and the sleeve 324 is a yieldableconnection so that sleeve 324 can override arm 320 when plate 338 ismanually operated. This yieldable connection comprises a plurality ofround headed studs 344, which are carried by a flange 346 projectingoutwardly from the sleeve 324, and engage holes 348 in a flange 350which extends outwardly from the sleeve 322. The sleeve 322 can movelongitudinally with respect to sleeve 324, but is normally held in suchposition that the studs extend into the holes by a compression spring352 received between the sleeve and a cup-shaped element 354 fitted onthe outer surface of sleeve 324 and held against movement toward theright by a spring retainer clip 356 which is received in a groove on theouter surface of sleeve 324.

The automatic movement of sleeve 324 through actuation of arm 320 isefiected by oil pressure operating through the piston 272 and controlledin a manner to be described. Means are provided, however, to rotate thesleeve 324 manually to effect a change in mixture setting in the eventof any emergency which might occur or'if the automatic device isdisabled through failure of oil pressure or for any other reason. Themanual operating means includes an annular element 360 secured to theperiphery of the circular plate 338 in any suitable way, or integraltherewith; and rotatably mounted thereon is a second annular element 362having an operating arm 364 integral therewith, said arm being adaptedto be connected with some suitable form of operating linkage whichextends to a lever in the cockpit to be operated by the pilot, theoperating linkage and lever not being shown herein.

The annular element 362 is retained between a flange 365 formed on theelement 360 and split-wire snap ring 366 which engages a groove in theelement 360 so that element 362 is movable only rotatably with respectto element 360. Means are provided, however, through which rotation ofelement 362 by its operating arm will cause a rotation of element 360,and through the plate 338 a corresponding rotation of the member 330 toeifect a change in mixture setting. For this purpose the element 360 hastwo lugs or teeth 368 which project radially inwardly into elongatednotches 370 formed in the outer surface of the element 360, as bestshown in Fig. 90. When the lugs engage the ends of the elongatednotches, the element 360 is rotated with the element 362, but about 30of lost motion are provided in which there may be relative movementbetween the two elements 360 and 362 before that one of those elementswhich is being moved can efiect movement of the other element. Theactual idle movement of either element 360 or 362 will depend, ofcourse, on the position of the two elements at the time movementactually starts.

With the mechanism described, if the arm 320 is actuated by the piston272, the mixture regulating element 330 will be moved until the lostmotion provided by the lugs and notches described is eliminated beforethere is any tendency to move the element 362 which is connected to themanual mechanism. After the lost motion is eliminated, there will be aforce applied to the element 362 and the manually operable control leverwill be shifted. If the automatic mechanism fails and the manuallyoperable lever is used to set the mixture control, the lost motion willbe first eliminated and then the yieldable connection will yield topermit movement of the control member 330 without corresponding movementof its actuating arm 320.

If desired, the notches 370 can be eliminated, so that the movement ofthe mixture control lever in the cockpit indicates the functioning ofthe automatic mixture control. Then the parts 338, 360, 362 and 364 canbe made integral.

As already stated, the pressure operated piston 272 is controlled in itsoperation by the periphery of the cam plate 234 which controls the pitchof the propeller. The cam periphery has two concentric surfacesdesignated by the reference number 380 and between these surfaces is adip 382, and these surfaces cooperate with the movable element of acontrol valve to determine its position. The valve comprises an outercylinder 384 which is fixed in position in a bore 385 formed in the wallof the housing section 24 and is provided with ports through which oilmay flow. An oil passage 386' communicates with said bore to supply oil.This passage 386 is formed in the housing section 24 and, when the partsare assembled in proper position, registers with the high pressure oilpassage 60, formed in the wall of housing section 2 and which suppliesoil to the main servo piston 34.

The outer surface of cylinder 384 is provided with three grooves 388,390 and 392, each of which communicates with one of a series of portsnumbered 394, 396 and 398, respectively. There are four ports in eachseries, but the number may be varied. The oil supply passage 386communicates with the groove 390, and the series of ports 3%, while anoil passage 400 formed in the wall of the housing, connects at one endwith groove 388 and ports 394, and at the other end with the cylinder274, at the right side of piston 272. Another oil passage 402 connectsat one end wtih groove 392 and ports 398, and at the other end with thecylinder 274 at the left side of piston 272.

Slidable Within the cylinder 384 is a hollow valve member 404, open atits lower end and urged upwardly into engagement with the cam peripheryby a compression; spring 406 received within the valve member betweenthe bottom of bore 385 and the upper end of the valve member which isclosed except for plurality of oil passages 408, that connect the spacewithin the valve member with the interior of housing sections 22 and 24in which the operating cam is located. An oil drain passage 410 (Fig.15) connects with the drain passage 95 in the bottom of the housingsection 2 to convey oil flowing from the cylinder 274 back to the sourceof supply, as shown in Figs. 5 and 10.

The valve member 404 has a series of holes 412 which communicate withports 394 and a series of grooves 414 arranged longitudinally of thevalve member which are of such length as to communicate with the ports-396 at all times and with ports 394 or 398 when the valve member 404 isin its upper or lower position, respectively. The passages 408 allow oilto flow from the interior of the member 404 to the interior of thehousing to be returned to the source of supply through passages 410 and95. V

The operation of the above described cam controlled valve mechanism isvery simple. Throughout most of the rotation of the cam the valve member404 is in engagement with the surface 380 which maintains said valvemember in its lower position, as shown in the drawings. Inthis positionoil under pressure enters the ports 396 and flows down the passages 414flows outwardly through ports 398 and passages 402 into cylinder 274 atthe left side of piston 272, forcing the piston to the position shown inFigs. 7 and 15. During this motion of the piston 278, the oil at theright thereof is forced through passage 400, ports 394 and 412 to theinterior of the valve member 404, from which point it flows throughpassages 408 to the space within the housing section 22, the ports 394and 412 being so positioned that they slightly overlap under theseconditions to permit a fiow of oil therethrough. With the parts in theposition described, the mixture control mechanism is moved by the piston272 to give a richmixture which is suitable for operation under mostoperating conditions.

If the cam is moved to a position where the surface 382 engages thevalve member 404, such member will be lifted by spring 406 to its upperposition. In such position, the ports 412 are out of registry with theports 394, but the upper ends of passages 414 have been moved intoregistry with the ports 394 and the lower end of such passages are inregistry with ports 396. Oil can then flow through said ports 396,passages 414, ports 394 and passage 400 to the right side of piston 272moving such piston to the left. As the piston so moves, oil to the leftthereof is forced through passage 402 into the space within member 404,and out of passages 408, the.

lower end of member 404 being above the edge of ports 398, to partlyuncover such ports when the member 404 is in its upper position. Themovement of piston 272 to the left sets the mixture control for a leanmixture.

It will be noted particularly that the control cam is positioned so thatthe surface 392 is engaged by valve member 404 only when the maincontrol lever 186 is set in position. to adjust the manifold pressurefor cruising, this being the only operating condition when it isdesirable to.- automatically position the mixture control mechanism fora lean mixture.

Regardless of what position the automatic control may occupy, themanually operable lever 3.64. may be moved.

by the operator at any time to adjust, the mixture control to giveWhatever mixture is necessary for proper operation of the engine. Also,in the event of any failure of the automatic device to operate, thepilot may use the manual device to adjust the mixture as desired. Itwill be apparent also that the automatic device sets the mixture controlin either one of two positions only, rich, if the piston 272 is at theright end of the cylinder 274, and lean, if it is at the left end of thecylinder.

The provision for manually overriding the automatic fuel-air mixtureratio selector, allows the pilot to vary the mixture at will or to cutofi the fuel supply when stopping the engine. Strictly the maintenanceof a given fuel air ratio is the function of the automatic meteringmechanism of the carburetor; the present device selects only whether theauto rich or the auto lean range of the carburetor is operative, thisselection formerly being under control of the pilot by the so-calledMixture lever in the cockpit.

Means are provided to prevent operation of the engine at a speed above amaximum predetermined speed in order to prevent possible damage whichmight be occasioned by too high speed operation. The means to accomplishthis result is a solenoid which is automatically energized when thespeed reaches the predetermined speed referred to and is effective tooperate the control valve for the main servo piston to cause the latterto move the throttle toward closed position. This movement of thethrottle will cause a reduction in engine speed which will deenergizethe solenoid when the speed is reduced sufiiciently to insure safety ofoperation.

The solenoid is best shown in Fig. 6, and comprises a casing- 420secured in any suitable way to a base plate 422 which, is secured to apart of the end plate 48 of the housing section 24 by the machine screws50 which hold the housing sections 2 and 24 together. Within the casing420 and insulated therefrom is a winding 426, lying between two endplates 428 and surrounding a brass tube 430 from which the winding issuitably insulated. Fixed within the tube 430 is the core 432 andslidable within the tube is the armature 434 provided with restrictedports 434a and attached to a rod 436 that ex" tends through the core andis directly in alignment with themovable element of the control valvefor the main servo piston. A compression spring 438 normally holds thearmature in the position shown in Fig. 6 and in which position it abutsa disc of insulating material 440. Leads 442 and 444 are connected withthe winding and a suitable cable armor (not shown) for enclosing theseleads is adapted to fit within the nipple 446 extending laterally fromthe casing 420. As shown in Fig. 15, leads 444 and 442 are. connectedwith a speed controlled switch and a battery 445. The speed controlledswitch may be of any desired form, a suitable design of switch beingshown in Fig. 12A and described briefly later.

Whenever the speed controlled switch is closed, the armature 434 movesto the left and rod 436 engages the tubular member 80 of the servocontrol valve, such member being always at or near its limit of movementto the right when the engine speed is sufiicient to energize thesolenoid. Rod 436 will, in this way, move member 80 toward the leftwhich will cause a movement of the servo piston toward the right,partially closing the throttle and effecting a reduction in enginespeed. When the speed is sufficiently reduced, the solenoid will bedeenergized and. the armature 434 will be moved back by spring 438 toits original position as shown in Fig. 6. This movement of armature 434is retarded by the dash pot provided by the armature, the tube 430 andthe disc 440, the ports 434a in the armature providing for a retardedtransfer of air. Therefore, the armature rod 436 does not release thevalve 80 as soon as the speed diminishes to open the speed controlledswitch. This feature is conducive. to astable operation of the automaticpressure regulator, thereby preventing the surging of the engine speedbetween limits above the predetermined maximum speed.

The speed controlled switch which is shown diagrammatically in Fig. 12Aincludes a shaft 450, which is driven by the engine at speeds which varyas the engine speed varies. A cup-shaped member 452, attached to theshaft 450, carries pins 454 which pivotally support weights 456 whichare normally held in the position shown in the drawings by springs 458received in recesses 460 in the weights and engaging the member 452.Each weight 456 carries a pin 462 which engages the flanged end 464 of asleeve 466 which surrounds the shaft 450 and is slidable thereon. Thissleeve may either rotate on the shaft or rotate with it. Secured in theend of the sleeve is a nonconducting button 468 which engages aresilient contact arm 470 fixed at one end to a suitable mounting 472and normally resting against a stop pin 474. The arm 470 carries acontact 476 which is movable by the button 468 into engagement with acooperating fixed contact 478 when the engine speed reaches apredetermined maximum and is disengaged therefrom by the inherentresiliency of the arm 470 when the engine speed drops oif to apredetermined extent. The switch contacts 476, 478 are connected onewith a battery 445 (Fig. 15) and one with wire 444 leading to solenoid416. Wire 4 42 connects battery 445 with solenoid 416.

Rotation of the shaft 459 causes Weights 456 to move on pivots 454, dueto centrifugal force, and pins 462 move sleeve 466 to the right so thatwhen the speed of shaft 45% attains a predetermined value, the button468 engages the resilient switch arm and closes the switch. As the speedof shaft 450 decreases following energization of the solenoid and theresulting deceleration of the engine, the switch is opened. The openingof the switch causes the de-energization of the solenoid 416 and therelease of valve 80 which moves toward a position for causing higherintake pressure and higher engine speed. This cycle is repeated so longas the speed of the engine tends to exceed the maximum allowable speed.The variation in speed warns the pilot that the propeller pitchcontroller is not working properly.

Figs. 16 and 17 are diagrams showing the mode of operation. In Fig. 17,curve a-b shows the relation of throttle opening to movements of mainlever 186 when the piston 34 remains at the right end of cylinder 36. Inother words, curve a-b shows the throttle opening which can be effectedmanually. For a particular type of engine, the throttle opens from idleposition to about a 40 position, while the lever 186 moves from aboutthe 1 position to the 39%. position. Curve a'-b of Fig. 16 shows thecorresponding manifold pressures obtainable at sea level.

The heavy located vertical line indicating the 13 position of lever 186is where a'-b intersects curve glzjk: and this 13 line shows the minimumsetting of lever 186 for obtaining full automatic control from sea levelupwardly. The heavy vertical line indicating the 33 position of lever186 and marked Military and take-cit indicates the position of thesetting of lever 186 required for Take-off. The heavy vertical lineindicating the 39 /2 position of lever 186 and marked Emergencyindicates the setting of lever 186 required for Emergency operation.

The movements of main lever 186 cause movements of earn 144 whichcontrols the datum of valve 80 which controls the servo which effects anopening of the throttle in addition to the opening effected by the lever186. If the can". 144 is set to give a maximum selected intake pressureof 52 /2" Hg, the degrees of cam movement corresponding to degrees oflever movement areshown by curve c d of Fig. 17. Curve e; of Fig. 16shows the relation of degrees of cam movement to engine intake pressurein inches of mercury (absolute). For example, movement of lever 186 to39 /2 position causes movement of cam 144 to about its 89 position, Fig.17.

. 12 According to point 3 of curve e--;f of Fig. 16, the 89 position ofcam 144 gives a maximum pressure selection of 52 /2" Hg.

The throttle opening obtained by manual operation plus maximum servooperation (piston left) corresponding to various positions of lever 186is represented by curve s-t Fig. 17. The maximum is approximately ofthrottle movement when the lever 186 is at the 39 /2 position and theservo piston is at the extreme left position. The differences betweenthe ordinates of curves s-t and a-b (Fig. 17) represent the range ofservo-piston movement to effect throttle opening in addition to thatobtained by manual operation. Curve s-t shows that the intake pressureregulator is not capable of producing maximum throttle opening whenpressure selections are below military power. Test work conducted on theengine under consideration indicates that, for all practical purposes,the critical altitude under (the above described) cruising and normalpower conditions is not reduced to an appreciable extent. It is possibleto design the controller so that the throttle valve will be fully openedat settings of the main control lever less than required for take-off.

It will be understood that whenever the pilot operates the main controllever to select some desired pressure for take-off, cruising, or otheroperation of the aircraft, the movement of the throttle valve to obtainthat pressure is partly manual and partly automatic. The operatingconnections beween the main lever and the throttle are such that whenthe lever is operated to select a pressure the throttle is never movedall the way to the position it must occupy to obtain the pressureselected. There is always an automatic movement of the throttle inaddition to the manual movement when there is an operation of the mainlever to select a pressure. After a selected pressure has been initiallyobtained, that pressure is maintained during operation of the aircraftat different altitudes entirely automatically without any manualmovement of the throttle.

Curve ghjk marked Selected pressure, 52 /2 setting, sea level" shows therelation between degrees of main lever movement and engine intakepressure selection for sea level operation. Pressure selection isobtained by movements of cam 144 which is moved by main lever 186. Whenlever 186 has moved to the 13' position, cam 144 has moved to its 36position, as noted on curve cd, Fig. 17. This gives a pressure selectionof 20" according to point 1 curve e-f, Fig. 16. Full automatic controlbegins here. Hence point h on curve g-]z-jk indicates 20" pressureselection when lever 186 is in the 13 position. When lever 186 is movedto its 33 or take-off position, cam 144 moves to its 76 position (Fig.17) which gives a selection of 45" pressure, as indicated by point 2 oncurve ef (Fig. 17) and point 1 on curve g-hjk. When lever 186 is movedto its 39 /2 or emergency position, cam 144 moves to its 89" position asindicated by curve c-d (Fig. 17) which gives a pressure selection of 52/2" as indicated by point i 3 on curve ef (Fig. 16) and by point It oncurve g-hj-lc. That part of the selected pressure curve between It andit represents the range of automatic pressure regulation at sea level,and upwardly, when the maximum pressure to be selected is 52 /2". Linen--0 represents the modification of the range of pressure selectionwhich, at sea level, is represented by h 'k, this modification being dueto the movement of eccentric 148 as the piston 34 moves toward the left.One advantage of this is to keep the I. M. E. P. (indicated meaneffective pressure) substantially constant with variation in altitude.In case of a single speed mechanically driven super-charger, thiscondition would give substantial constant power independent of altitude.Another advantage of the action of eccentric 148 is the stabilization ofthe operation of the automatic regulator.

Curve a'h shows on account of its up and down character that thepressure cannot be controlled by the auto-. matic pressure regulator.Therefore, pressures along a'h are obtained only manually by the mainlever movement only. This is done by making the pressure selection curveg-h lie well below a'h, while this unstable condition occurs in theengine. To the right of point h, the manifold pressure steadilyincreases with throttle opening, this being necessary in order to insurestability and prevent hunting.

Whenever possible, point g should be 30" to 35" Hg, below idling intakepressure since breakage of the aneroid bellows 196 (Fig. will cause thepressure selected by cam 144 to increase by atmospheric pressure. Tomake it possible for the pilot to close the throttle with a brokenaneroid, the lowest selected pressure, when the aneroid bellows 196 isbroken, should be no greater than idling pressure. In the disclosed formof the invention, if the aneroid bellows 196 were broken, the selectedpressure would be according to line l-m in Fig. 16 which is 30" Hg aboveg-h. Therefore, movement of the main control lever 186 to 0 positioncauses the intake pressure to become the value I which is substantiallythe same as value a at the left end of curve a-b'. Therefore, the pilothas complete control of the engine throttle for landing purposes.

When the connection between link 172 and arms 180 and 160 is as shown inFig. l, the cam 144 will select pressures up to 52 /2" Hg. When theconnecting pins 176 and 168; pass through holes in arms 180 and 160other than as shown, the cam 144 will select pressures up to maximumother than 52 /2". For example, when pin 176, passes through uppermosthole 178 of arm 180 and when pin 1 68 passes through the lowermost holeof arm 160, the earn 144 will select pressures up to 65" Hg.

Then the movement of the cam 144 is related to the movement of lever 186as indicated by line c'd (Fig. 17), the selected pressure will be asshown by line g-h'k'; and the selected pressure with broken aneroid willbe as shown by line l'm in Fig. 16.

Line p-r (Fig. 17) shows the relation between movement of lever 186 andselected engine or propeller R. P. M. as determined by cam 238. This istypical of one particular engine and may vary with different types ofengines.

Line uv.wxy-z (Fig. 17) shows the relation between movement of lever 186and the automatic rich setting and the automatic lean setting of thecarburetor as determined by cam surfaces 380, 382.

Fig. 18 is a diagram showing various positions of the mechanism forcontrolling the position of the throttle valve v. The various links,rods, levers and pivotal connections are numbered with the referencenumbers applied to the parts illustrated in the preceding figures, Whencontrol lever 186 is at 0 or 1861 position, the other parts are locatedin the positions indicated by subscript number 1. Pivot 17a is at 17111;differential lever arms are at 281 and 141; link 30 is at 301; link 12is at 121; throttle shaft arm a is at an; and throttle valve v isat v1which is idle position.

Movement of lever 186 from 0 or 1861 position to 33 or 1862 position,required for take-off (Fig. 17), causes the pivot 17a to move to 17112and the differential lever arms 28 and 14 to move to 282 and 142respectively. Link 30 moves to 302. Link 12 moves to 122, arm a to a2,and valve v to v2 which is the 32 position as indicated by the chart(Fig. 17 at point v2 where curve 11-!) crosses the 33 vertical linemarked Take-off. Movement of lever 186 to 1862 also causes such movementof the cam 144 as to cause the selection of 45" Hg intake pressure asindicated at i of curve ghj-k (Fig. 16) where that curve crosses the 33or Take-off line. Piston 34 moves toward the left to cause such furtheropening of valve v as necessary to maintain 45 Hg pressure in the engineintake. To insure that manifold pressure at sea level does not exceedthe selected value.

45" Hg for example, even under conditions giving a dynamic ram of air atthe entrance of the intake system due to the forwardly projecting airscoop and high air-. plane speed,'it is arbitrarily arranged thatopening of the throttle by direct manual linkage is insuflicient, evenat sea level, to give the selected pressure and that, in conse quence,the throttle must be additionally slightly opened by the servo-piston34. This provides the desired margin so that the piston 34 floats offits right end stop and can maintain pressure by motions in eitherdirection.

As altitude increases from sea level, the movement of piston 34increases. At critical altitude, the piston, 34 will have moved toextreme left position 343, thereby causing link 30 to move to 303 anddifferential levers 28 and 14 to move to 283 and 143, respectively, link12. to move to 123 arm a to move to :13 and valve 12 to move; to vswhich is its 77 position which corresponds to point 1 3 on Fig. 17,where curve s-t crosses the 33 or Takeoff line.

Point 1' on curve p-r together with point k on curve gh-j-k representsthe conditions for maximum power at sea level. For example, the speedfor engine maxi: mum power for 52 /2" selected pressure is 2800 R. P. M.engine speed at sea level according to curve pr. Engine criticalaltitude, when a mechanically driven supercharger directly connected tothe engine is used, is greatest at, engine maximum speed. This is 3000R. P. M. engine speed in the engine under considerationand correspondsto a setting of lever 186 between its 33 and 36 /2" positionsapproximately.

Therefore, in order to make an emergency flight, the pilot sets lever186 at 1864 or the 39 /2 position, thereby moving pivot 17a to 17m andthe differential lever to 14s and 284, link 12 to 124, arm a to at andvalve v to v4 or about the 40 position. This movement of lever 186 setscam 144 to select a pressure of 52 /2 Hg. As the altitude increases,piston 34 moves left and causes the differential lever arms 28, 14 torock about their pivot 17m from the positions 284 and 144 respectivelyto positions 28X and 14;; respectively, the corresponding position ofthe piston 34 being 34X. When piston 34 arrives at 34X the tail 28a ofthe differential lever will have arrived at 28cm (Fig. 20) wherein itjust touches stud 20a of' shaft 20. At the same instant, arm a is at axand valve v at vx or about the 81 position. Further movement of piston34 to 345, at the extreme left in Fig. 18, which is attained at thecritical altitude for the 52 /2" Hg pressure setting, causes thedifferential lever 14, 28 to pivot around the stud 20a and not the pivot17a. Therefore, pivot 17a moves from 17114 to 17:5, the differentiallever 28, 14 moves from 28X, 14;; to 285, 145, link 12 moves from 12;;to 125, arm a from ax to as, and valve v from vx to v5 which is the 79position. As pivot 17a is kicked back from 17th; to 17x15, shaft 20 mustmove the same angular distance which is about 3. Cam 238 (having 5 to 1ratio with shaft 20) moves 15 which causes the speed selection to changefrom 2800 R. P. M. to 3000. R. P. M. The kicking back of shaft 20 causesa clockwise movement of cam 144 which moves to a position correspondingto the 36 /2 position or the 1865 position of lever 186. This gives apressure selection of about 48" Hg which is safe to use when the enginespeed is 3000 R. P. M. in order to attain an altitude higher than thecritical for the 2800 R. P. M. and 52" Hg pressure selection.

Fig. 181. shows graphically the function of the kickback. Curve A--B-Cshows the relation of propelling horsepower and altitude for engineoperation at 2000 R. P. M., 52 /2" Hg intake pressure; and curve DE.Fshows that relation for engine operation at 3000 R. P. M. and about 48"Hg intake pressure. The ascent; is made according to curve A-B. Whencritical altitude B is reached, a shift is made during the kick-back ofdifferen-. tial lever pivot 17a from 17am to 17:15 (about 3) from. Boncurve A-B-C to E on curve D-E-F so that the altitude E (higher than B)can be attained before propelling horsepower decreases appreciably. Theengine can be safely operated in an emergency at a speed increased to3000 R. P. M. and at intake pressure reduced to about 48" Hg. This showsthat a rapid ascent can be made without overloading the engine until acertain high altitude is reached. Then to go higher, the engine can betemporarily crowded or speeded up without danger of overloading, sincethe intake pressure is reduced. By following this procedure of enginecontrol, the engine will stand up under a number of emergencies greatlyexceeding the number which would obtain where it is attempted to climbat maximum speed.

As stated before, lever 186, which is represented diagrammatically inFig. 18 as one lever, is in fact a divided lever system comprising anarm 186a journalled on shaft and operatively connected with an arm 186i)fixed to shaft 20 by a compression spring 480 (Fig. 1). Therefore, whenarm 186i) is kicked back to 1865 (Fig. 18) while the pilot maintains thearm 18612 in the 39 /2 position (or 1864 in Fig. 18) the spring 480 iscompressed. When the emergency is over and the pilot causes the arm 186ato return to the 33 or military position, the arm 186b does not back-up6 to its Bil /2 position, but returns to its 33 position also, becausethe spring 480 is permitted to expand to restore to normal the angularrelation between the lever arms 186a and 18Gb. The spring 480 has forcesufiicient to control the cam 238 which efiects selection of engine orpropeller R. P. M., so that this selection will be at 3000 R. P. M. asthe lever system 186 returns to military position.

Fig. 19 is a diagram showing the pilots control lever 500 located in thecockpit for controlling the main control lever 186 (which in factincludes arms 186a and 18Gb as previously described, but which is showndiagrammatically as a single lever). Lever 500 comprises a knob 501integral with a tube 502 attached to a toothed block or detent 503 forengaging a toothed segment 504 on a stationary sector 505. Tube 502 isslidably supported by a lever rod 506 having a head 507. Between head507 and a plate 508 on the interior of knob 501, there is located aspring 509 which urges the knob 501 and the detent 503 upwardly toengage the segment 504. The lever rod 506 has a hub 510 pivoted on a pin511 carried by sector 505 and is connected by link 512 with lever 186.

Depression of knob 501 is required before the lever 500 can be movedfrom 0 position to the 33 position, or to intermediate positions.Release of knob 501 permits detent 503 to engage the toothed part ofsegment 504 so that the lever 500 will remain in its 0 or 33 positionsor between them. Before moving lever 500 into 39 or emergency position,knob 501 is pressed. As the lever S00 is so moved, rod 506 which is at5060: in the 33 position of lever 50%, pushes against a pad 520 urged bya spring 521 toward the right; and spring 509 pushes detent 503 againstthe smooth part 513 of segment 504. Therefore, the pilot is required tohold the lever 500 in emergency position. When the emergency is over,the pilot releases grasp of the lever 500, whereupon the spring 520expands to force lever 500 to the 33 position, where it is held by there-engagement of detent 503 with the toothed part of segment 584.Therefore, the pilot is not required to remember to restore the cockpitlever 500 to military or take-off position when the emergency ceases.

In case the controller is damaged so that piston 34 sticks and does notreturn to right position by spring 38, provision is made for moving thethrottle valve manually to a closed position suflicient for landing.

' For example, if the piston 34 were stuck at location 34' (Fig. 19)throttle valve v would be in partly open position v. To move the valveto idle position v, the knob 501 is depressed and the lever 500 is movedto 500 or position, thereby causing the throttle Valve 16 to move from vto v. Therefore, the pilot can move the throttle valve to idle position.

Re'sum of advantages Most airplane engines have a supercharger directlydriven by the engine which delivers to the manifold, air or air and fuelmixture under pressure. charger is made to give the desired intakemanifold pressure at the rated altitude, consequently below ratedaltitude the intake system has to be throttled down to preventoverboosting and serious mechanical damage to the engine. Without meansof controlling manifold pressure independently from altitude, the pilotis compelled to operate the throttle as the altitude changes, this beinga serious handicap on millitary or commercial airplanes. This handicapis eliminated by the present engine controller. All that the pilot isrequired to do is to move the cockpit lever 500, which shifts the maincontrol lever 186 of the controller, to the desired position, such asidle during the warm-up period, and to take-0E when it is desired toleave the ground. Movement of the lever 186 causes the throttle valve toopen part way and the servo piston 34 of the automatic regulator movesleft to effect whatever additional opening of the throttle is requiredto obtain the manifold pressure selected for take-off. As the planeascends, the piston 34 moves left to cause the selected manifoldpressure to be maintained in a predetermined relation to altitude. Ascritical altitude is approached, the selected pressure is graduallydecreased below that selected at sea level, due to the action ofeccentric 148, in order to maintain a substantially constant indicatedmean effective pressure. The earn 144 in fact is designed to give apressure which is slightly in excess of the pressure selected bymovement of lever 186. But,

' as the piston 34 moves left, a correction is made by the accompanyingmovement of the eccentric 148. Another advantage of this action is toproduce stability of operation of the automatic pressure regulator.Hunting is substantially eliminated.

During descent the piston 34 moves right partly to close the throttle towhatever position is required to maintain the selected pressure in apredetermined relation to altitude.

Another important advantage is that the pilot can operate the throttlemanually in case of failure of the automatic pressure regulator andfailure of the servo piston 34 to move from its rest position, thelinkage having been so constructed that the pilot can open the throttlemanually to obtain nearly full power at sea level. In case of oilpressure failure when piston is at left, spring 38 will return piston 34to the right or rest position to give the minimum throttle opening thatcan be effected by the automatic pressure regulator. This is done toprotect the engine from immediate failure in case the oil system isdamaged, while permitting the pilot to obtain adequate throttle openingfor landing. In otherwords, take-oil. can be performed independently ofthe condition of the automatic pressure regulator. If after taking off,the pilot finds the plane is unable to rise with adequate or properpower, he knows that the automatic pressure regulator is not operatingand he can safely land since he has sufficient manual control of thethrottle valve.

In case of breakage of the aneroid bellows thereby causing the selectedpressure to be increased by atmospheric pressure, the pilot can closethe throttle valve manually by moving lever 186 to the 0 position, whichmovement causes such movement of cam 144 as will bring the selectedpressure of the earn 144 to point g on the drooping line g-h (Fig. 16)which is 30" Hg below I on curve l-m, the result being that the pressureis at a on curve a'b'.

In case of sticking of the piston 34 to the left of its rest position,the throttle can be closed sufficiently to elfect a safe landing bymoving the pilots control lever The super-

